A SIMPLE HAND-HELD PUSH-BUTTON DEVICE FOR IN-SITU CALIBRATION OF PNEUMOTACHOGRAPHS

A simple and compact flow calibrator has been devised for generating p recise predetermined constant flow rates for checking the calibration of laboratory and clinical flow transducers used in respiratory measur ements. The standard version delivers preset flows of 0.5 and 1 l/s, w hereas a tuned-up version can produce preset flows of 2.5 and 5 l/s, w ith an accuracy of +/-2%. The pressure generated is sufficient to cope with most commonly used respiratory flowmeters. The flow calibrator i s built from inexpensive components that are readily obtainable: a fan , a turbine flowmeter, and a feedback circuit in a compact housing. Th e device is easy to connect to other equipment and to operate. Three f low calibrators have been built and are in regular use in a lung funct ion laboratory and on intensive care wards.